Structural analysis of CLT multi-storey buildings assembled with the innovative X-RAD connection system: Case-study of a tall-building

The cross laminated timber (CLT) technology is nowadays a well-known construction system, which that can be applied to several typologies of residential and commercial buildings. However some critical issues exist which limit the full development of the CLT construction technology: problems in handling, difficulty in assembling and inadequate connection systems. The connectors that are usually adopted in CLT structures, derive from the light timber frame technology and consequently might prove inadequate when employed in tall buildings (over 6 floors). The structural design of CLT structures is also problematic because of the complexity in verifying the connectors and in defining the actual load path within/between the panels. The various connection systems, e.g. hold-downs, screwed-in elements and metal brackets are all to be nailed onsite, with ensuing uncertainties related to the use of different connection systems and to the "hard-to-verify" quality of the onsite instalment operations. An innovative connection system specifically designed for CLT structures, such as X-RAD, was analysed. The X-RAD system is characterized by a single standard connector to be placed at the corners of the CLT panels. The connector is formed by a metal box containing a pre-drilled hardwood insert that allows attaching the connector to the panel with fully threaded screws inserted at different angles. A case study of a multi-storey building was selected in order to investigate the structural behaviour of the X-RAD system and to exploit the potential of this system applied for assembling tall timber buildings.